Factor of interfacial potential for the surface plasmon-polariton resonance sensor response

Abstract

In this work, we investigate how the application of an external potential difference to the sensitive gold-electrolyte interface influences the optical response of a sensor based on the surface plasmon-polariton resonance (SPPR). The SPPR resonant angle shift was registered for an aqueous solution of sulfuric acid as an electrolyte at different potential sweep rates. From the measurements of SPPR curves versus the applied voltage, the potential of zero charge of the gold electrode in the electrolyte solution was estimated. To explain the external voltage influence on the SPPR sensor response, a theoretical model was used that takes into account three factors: free electron concentration change in the space-charge layer (SCL) in the surface layer of gold, dependence of the capacity of electrical double layer at the interface on the voltage, and gold film surface roughness.